1. Field of the Invention
The present invention generally relates to converting a precursor into a ceramic and, in particular, to a process for conversion bonding disparate graphite components into a single, unitary silicon carbide monolith ceramic such as a scan mirror formed from more than one piece.
2. Description of the Related Art
Laser scanners use an oscillating or rotating mirror to reflect a beam of laser light onto a target, for example, a barcode, and a photocell receives the reflected light. The scanners may have one mirror that sweeps in only the horizontal or vertical direction, or the scanner may have two mirrors that sweep the beam in both horizontal and vertical directions to create a grid of scan lines. This type of scanner is the one most often used in retail checkout lines, the advantage being that the chances are good that at least one of the scan lines will get a clean read of a barcode. Thus, the operator does not have to aim the scanner or carefully position the barcode.
The scan mirrors are typically formed as a one-piece design by machining or casting a material, silicon carbide (SiC) being a commonly used material. In addition, mirrors may be machined from a precursor, such as graphite, and then converted to a ceramic, such as silicon carbide. Silicon carbide satisfies the requirements for scan mirrors, which include low mass and high strength, allowing the mirrors to be rotated at high speeds. The mirrors are constructed to have an optical section, which has a reflective face, and a support section, which has a mounting bracket for mounting the mirror to the drive apparatus of the scanner.
The current methods of forming scan mirrors have several problems. One problem of the current methods of forming scan mirrors is that the mirrors have a tendency to fail at or near the mounting bracket. The optical and support section are formed as one unit, and this may lead to engineering compromises for the mounting bracket. Also, the method requires a separate mold or machining process for each mirror, based on the size, shape, orientation of the reflective face and on the drive apparatus to which the mirror will be mounted.
Thus, there is a need for an improved scan mirror and method of construction, in which the optical and support sections of the mirrors are formed separately from a precursor material and assembled prior to conversion to a ceramic. There is also a need for a method of constructing scan mirrors, in which a support section adapted to be mounted to a given drive apparatus may be assembled to any of a plurality of optional optical sections that vary in size, shape, or orientation prior to conversion to a ceramic.